Heating and ventilating system



Nov. 21, 1933. w. SHURTLEFF 1,936,544

HEATING AND VENTILATING SYSTEM Filed Jan. 51, 1931 p I2) MIMI IIIIII Patented Nov. 21, 1933 HEATING AND VENTILATING SYSTEM Wilfred Shurtleff, Moline, 111., assignor to The Herman Nelson Corporation, Moli ne, 111., a

corporation of Illinois Application January 31,

5 Claims.

This invention relates to improvements in heating and ventilating systems.

In accordance with the most improved modern practice in heating and ventilating, it is desirable as a rule to admit outdoor air only in sufficient quantity to prevent overheating of the room, and only at times when the supply of steam or other heating medium to the radiator has been cut off, and for the purpose of reducing the effect of body heat given off by the occupants of the room, or other uncontrollable causes.

It has further been found that it is unsatisfactory to rely entirely upon thermostatic means responsive to room temperature to control the admission of fresh outdoor air, since in freezing weather the ingress of outdoor air admitted through dampers responsive to thermostatic control at room temperature will tend to cause drafts and streaky conditions within the room, so that in such conditions of prospective overheating it is better practice to shut off the supply of heating medium to the radiator and to recirculate the indoor air exclusively until the outdoor temperature has warmed sufiiciently during the progress of the day to warrant .the admission of exterior air for tempering purposes.

It has been found in practice that the admission of exterior air delivered from the outlet of the unit heater andventilator at a temperature of from fifteen to twenty degrees below room temperature can be safely provided for, but that a difierential of thirty degrees between the air so delivered and the room temperature constitutes about the limit at which exterior air can be safely admitted.

Practical tests in well built school rooms indicate that no arificial heat is neededwhen outside air is over sixty degrees on cloudy days, or over fifty degrees when the room is exposed to full radiant sun effects. The excess body heat of a room of standard seating capacity for pupils during usual periods is equal to the heating eifects of approximately forty feet of cast iron radiation. Direct sun rays into the room from all windows may equal five to forty feet of radiation in addition, varying in the intensity of the sun rays absorbed by the interior surfaces of the room.

It thus appears that the heating of a school room or similar place of assembly is due only in part to the maintenance of artificial heating and in these conditions it is desirable to provide for the ingress of outdoor air when conditions warrant, for thepurpose of avoiding overheating, and to rely on re-circulation of indoor air to maintain comfortable conditions within the room 1931. Serial No. 512,563

when exteriorair is not required for cooling purposes.

The object of the present invention is to provide apparatus operable in conformity with the above requirements, which includes thermostatically controlled means for admitting outdoor air when warranted by outside temperature conditions, in conjunction with thermostatic means responsive to room temperature for controlling the supply of heating medium to the radiator. By providing an appearatus subject to this dual meth- 0d of control, the supply of heating medium and the supply of fresh air will be independently regulated in such a way as to maintain comfortable living conditions within the room, to conserve the fuel supply, and to avoid danger or discomfort occasioned by the admission of outdoor air at an excessively low temperature.

Further objects and details of the present invention will appear from a description thereof in conjunction with the accompanying drawing, wherein- V Figure 1 is a sectional elevation of a unit heater and ventilator embodying the principles of the present invention; and A Fig. 2 is a detail showing the air inlet with the thermostatic bulb employed for controlling the operation of the damper thermostat.

The unit heater and ventilator shown in the drawing serves merely to illustrate the principles of the present invention, and numerous variations in structure may be introduced without departing from the spirit of the invention.

As shown, the unit comprisesa housing 10 which, as usual, is of rectangular boxlike configuration and is partitioned oif on the interior to provide a heating chamber 11 near the upperpart of the housing, beneath which is a blower chamber 12 having mounted therein a fan unit 13 which includes a motor 14 for operating the fan.

In the front wall 15 of the housing near the base thereof is a re-circulating air inlet 16 which delivers air from near the floor of the room to the blower chamber. Immediately opposite the re-circulating air inlet, and in the rear wall 17 of the housing, is located an exterior air inlet 18 which communicates with a fresh air chamber 19 protected by fixed louvers 20.

As shown, the re-circulating air inlet is provided along its upper margin with an obliquely inwardly extending flange 21, and the outdoor air inlet is similarly provided with a flange 22, and between the flanges is hinged a damper 23 which is shown in full lines in intermediate position, but which may be swung forwardly or rearwardly to occupy eitherone of the dotted.

line positions shown for the purpose of closing either the re-circulation air inlet or the outdoor inlet as occasion may require.

The heating chamber 11 has located therein a light weight radiator 24, which is preferably of the non-ferrous type having a relatively large radiating surface of the kind commonly employed at the present time in unit heaters and ventilators. The heating medium, as for instance steam, is admitted through a valve 25, conventionally shown in the drawing, which valve is thermostatically operated from a room thermostat 26 connected by a tube 27 in the usual manner. The conditioned air is upwardly discharged through a discharge outlet in the top of the housing protected by a grille 28.

The damper 23 is operated by a motor 29 which is connected by a link 30 with the damper; and the operation of the motor is controlled by a thermostatic bulb. 31 located at the entrance to the fresh air chamber 19 and shielded and partially protected by one of the louvers 30. The bulb is connected with the motor by means of a flexible tube 32, the arrangement being such as to permit the distance between the bulb 'and the motor to be varied to conform to local requirements without modifying the operation of the device.

The thermostatic bulb and the flexible tube will be filled with some expansible fluid responsive to thermal variations, and as the temperature rises and the fluid expands, the motor will act to swing the damper to the right and into position to abut against the flange 21, and thus close the re-circulating air inlet, while under lowering thermal conditions .a movement in the reverse direction will take place, which finds its limit when the damper has been swung to the left and into position to contact with the flange 22, and thus close the damper against the admission of fresh air. Under normal operating conditions, the damper may occupy an intermediate position to proportion the amount of indoor and outdoor air admitted to the housing and subject to the suction of the fan.

In order to permit regulation of the action of the damper, a rather stifi coil spring 33 is provided which is connected at one end to the rear wall of the housing andconnects at its other end to an adjusting screw 34 entered through the damper, which permits the tension of the spring to be regulated and thus affords a separate and convenient means for adjusting the apparatus to operate at a predetermined exterior temperature.

It will be understood that the various devices shown in the drawing are represented more or less diagrammatically and that it is not the intention to limit the present invention to the'use of any particular form or arrangement of motor, thermostats, or other operating features, which are of a character well understood in the art and need not be described in detail;

It will be further understood that the unit heater and ventilator of may be used as the sole means for heating and ventilating a room, or that it may be used in conjunction with and supplementary to direct radiation, which latter method of heating is preferred in the case of large school rooms or other places of assembly.

In use, with the damper spring regulated to resist the operation of the motor at any outdoor temperature below fifty degrees, the damper will close the outdoor inlet during the early moming hours, during which time the interior air will be re-circulated until the temperature has risen to a predetermined degree, due to the giving oif of heat from the bodies of the occupants or to the effect of the suns radiant heat admitted to the room, at which time the indoor thermostat will operate to close the radiator valve and cut off the supply of heating medium to the radiator.

If thereafter the exterior temperature rises sufliciently, the damper controlling thermostat will act to move the damper sufliciently to admit a proportionate amount of exterior air, or even to completely close the re-circulation air inlet, so that in the latter condition, exterior air tion of the thermostat in opening the damper to increase the volume of fresh air admitted to the room for cooling and tempering purposes.

In extremely cold weather, it is rarely desirable to admit exterior air, since there is always a certain amount of leakage into-the room, and 4 .under these conditions a rapid re-circulation of the present invention interior air will promote the comfort of the room occupants, and the regulation and control of the radiator valve will prevent overheating, and by proper adjustment of the room thermostat and .5 the damper thermostat the admission of exterior air can be provided for when weather conditions warrant and at an exterior temperature which will guard against the admission of excessively cold air in quantities suflicient to occasion a streaky or drafty condition within the room. In cloudy weather, it will be desirable to so tension the damper spring as to prevent the opening of the exterior air inlet until the exterior temperature has risen to fifty or sixty degrees,

but in sunny weather the damper spring may be adjusted to permit the damper to respond tothe action of the thermostatically controlled motor when the exterior temperature stands at from forty to forty-five degrees, owing tothe superior heating effect of the radiant sun heat in rapidly raising the room temperature. The complete operation of the damper in swinging from one extreme position to the other will require moderate range in exterior temperature variation, so that under normal conditions the damper motor may, for hours at a time, maintain the damper in an intermediate position with the heating medium shut off and a mixture of, indoor and outdoor air admitted to the fan for circulation throughout the room.

The apparatus should be adjusted with the end in view of cutting oif the supply of heating medium to the radiator before any exterior air is admitted to the room, although occasional re: adjustments of the thermostatic controls may be necessary to maintain a harmonized relation between the two controlling members, but by so doingfuel will be conserved, a more rapid heating of the room in cold weather may be attained, and drafty conditions prevented.

I claim:

1. In a heating and ventilating system, the combination of a unit heater and ventilator comprising a housing having located therein a fan and a heating element, and having a re-circulating air inlet, an external air inlet, and a discharge outlet, means for controlling the intake of air from the air inlets, a thermostat for reglating the admission of a heating medium to the heating element, said thermostat being located within the room being conditioned, a duct leading from an external source to the fresh air inlet, and thermostatic means located cin position to be partially shielded from the direct action of the sun and adapted to control the action of the air admitting means in conformity with predetermined external air conditions.

2. In a heating and ventilating system, the combination of a unit heater and ventilator comprising a housing having located therein a fan and a heating element, and having a re-circulating air inlet, an external air inlet, and a discharge outlet, means for controlling the intake of air from the air linlets, a thermostat for regulating the admission of a heating medium to the heating element, said thermostat being located within the room being conditioned, a duct leading from an external source to the fresh air inlet, and thermostatic means located in said air duct and adapted to control the action of the air admitting means, and a shield positioned to protect said thermostatic means and to intercept the a motor for actuating said damper means to proportion the admission of exterior and interior air, an external air duct leading to the external air inlet, louvers for protecting the inlet to said duct, a thermostatic element located adjacent to the external air inlet and within said louvers and partially shielded from the sun by one of said louvers; a connection between said thermostatic element and said motor for actuating the motor responsively to the action of the thermostatic element when outside temperature is above 40 F.

4. In a heating and ventilating system, the combination of a unit heater and ventilator comprising a housing having a recirculating room air inlet, an external air inlet, a fan and a heating element located within the housing, damper means adapted to regulate the recirculation of room air and the admission of exterior air, a motor for actuating said damper means to proportion the admission of exterior and interior air, and a thermostat adapted to control the admission of heating medium to the heating element, said thermostat being located in a position to respond to temperature conditions within the room being conditioned to shut off the supply of heating medium after the room temperature has risen to a predetermined degree, a second thermostatic element located within the line of flow of the eternal air admitted through the external air inlet, and responsive in varying degreeto variations in the temperature of the external air throughout a range whose lower limit is substantially below that of the intended room temperature and adapted to correspondingly control the motor to impart fractional adjustments of the damper for varying the proportion of indoor air and external air admitted and for completely closing the damper against the admission of external air when the external temperature falls to the lower limit of the range of variations to which the last named thermostat is operatively responsive and for completely opening said damper when the external temperature rises to the high limit of said ranges.

5. The method of maintaining a satisfactory temperature within a room, which consists in constantly maintaining a circulation of air therethrough and in confining such circulation exclusively to room air when the temperature of the external air falls to a predetermined low degree, and in admitting external air when at a higher temperature, the proportionate amounts of external air admitted and room air recirculated being in ratio to variations in the temperature of the external air within a range whose low limit is the low temperature required to cause complete exclusion of external air the admission of external air being maintained at a maximum when the external temperature rises to and beyond the high limit of said range, and in artificially heating the air circulated through the room when the room temperature falls ,below a predetermined degree and in causing cessation of said artificial heating when the room temperature rises to said degree.

WILFRED SHURTLEFF. 

